The movie opens with a shot of a busy road, and a big building. Ash and the gang (Misty and Brock w/ Pikachu, Togepi, and their Pokémon) are going up an elevator, in the big building. Pikachu sees a Pichu, which makes a funny face at him. Pikachu makes one back, but its gone by then. They get to the top, and they let out their Pokémon to play. Ash tells the Pokémon that he will be back at 6:00, and now its 10:00.
After that's over, all of the Pokémon are playing around, when Pikachu sees the Pichu again, which makes a face, and slaps his own butt. Another Pichu comes out, which is the others Brother. Both Pikachu and the Pichu are on separate buildings, about 20 ft from each other. One of the Pichu almost falls, so Pikachu decides to take action, and starts to run down a little bit, grabs onto a pole, and gets ready to save Pichu, just to find out that Pichu was just helped up by his brother. Pikachu looks down, and he realizes that he is on a pole, about 30 stories up from the street.

Some Murkrow start to come over and bug Pikachu, pecking him, because he is on their territory. Pikachu grabs onto a clothesline that connects the two buildings, but the Murkrow start to peck at him, and he almost starts to fall off. On the building across from Pikachu is Meowth, working a Part Time job as a window washer. He looks over, and sees Pikachu, but guesses that he is just dreaming. Right before the Murkrow almost peck Pikachu down, the wind starts up, and about 40 Hoppip come, and float in the air. Pikachu starts to jump from one to the other, and then uses the small platform that Meowth is on as a springboard, springing Meowth very, very far away.

He's now is on the other building, with the Pichu. He yells out to the other Pokémon, but is drowned out by the traffic. The Pichu motion for him to come with them, so he runs along with them. They go through a small grate, and find themselves on top of an elevator, going down. When it stops, they go into the Air Conditioning vent, and drop about 30 feet, before rolling onto the top of a truck, where the AC vent ends. They use the truck to transport themselves, riding on the top, but at a sharp turn, they get thrown off, because they can't balance anymore. They find themselves in a small body of water, going through the city. They cling to a wooden rafter, which lets them float. Suddenly, they see something that looks like a giant Lapras, but it is a large cruse boat, heading straight for them. Pikachu starts to push the rafter as fast as he can, swimming. When they are about to hit the boat, a Gyarados comes from nowhere, and makes them skyrocket up, landing on a Houndour, which causes him to start chasing them. They climb up a pole, and go over a fence, but the Houndour climbs over. The end of the pole comes, but when they go down, they get to a fence. Cornered, the two Pichu decide to use Thundershock, which completely tires them out, and barely effects the Houndour. Pikachu has nothing to do, except to try to climb over the fence with the two asleep Pichu, which he eventually does. He jumps on another fence, and jump down, hoping for a miracle to happen, because there is an even higher fence right next to them, which they cannot climb over. They jump down, but they hit a Snorlax, which they easily bounce off of, and go to the next fence. The Houndour tries to copy them, but when he jumps down, nothing is there, because the Snorlax decided to roll over. He rolls back to where he used to be, on top of the Houndour.

Once the Pichu wake up, Pikachu and the Pichu find themselves in a tire yard, where many tires are made into a play fort, held down by many ropes. Many Pokémon jump out, and do a little dance scene. After that, the Pokémon leave, but then, Pikachu hears the clock chime 5:00. Right as that happens, he also sees the Houndour, which results in another chase around the Tire fort. Suddenly, some of the tires start to come loose, and land on the Houndour. Pikachu and the two Pichu save the Houndour, but as that happens, even more tires become loose, and the whole structure almost comes apart, but then, while Houndour holds one part of the structure, Pikachu goes to hold together one of the ropes that holds the Fort together, which starts to rip. The Pichu call out to the other Pokémon, which start to come, and help Pikachu and Houndour. They start to try to repair the building, but the rope that Pikachu and the other Pokémon are trying to hold together snaps. Right before the whole thing almost falls, the Houndour jams another tire in between one of the broken links, and holds it together for a few more minutes. The Pokémon all start to pile up the tires, trying to stabilize the building, and finally fix it.

After that, Pikachu says bye to everyone again, and makes friends with the Houndour. Pikachu sees the clock, about 20 minutes away from 6:00, when he has to be back!! He starts to run back, but then the Pichu come beside him, in a rolling tire, which he gets in. Very fast, they start to roll downhill, through traffic, and into Meowth, before getting into the hotel. Pikachu then says Goodbye to the two Pichu when he gets to the top, just in time. Ash comes back, and tells all of the Pokémon to go into the party room of the building, which they all find a big party laid out for them. Pikachu doesn't know what its for, but then Ash picks him up, and tells him that it is the anniversary of when they first met. All of the Pokémon are now happy, pigging out on cake, and Pokémon food. As Ash puts his cap on Pikachu, they all look outside, and see fireworks going off.